La Plata County officials’ independent study of water samples taken from the Animas River are in line with data published by the Environmental Protection Agency.
While doing remedial work at the Gold King Mine north of Durango on Aug. 5, an EPA-appointed team accidentally caused about 3 million gallons of heavy-metal laden wastewater to spill from the mouth of the mine and seep south down the Animas River.
In the wake of the spill, La Plata County contracted specialists to conduct an independent study of metal levels in the river to gauge and better understand the EPA’s findings.
Commissioner Gwen Lachelt told The Durango Herald in a previous interview that she hoped the results would quell concerns of citizens who distrust the EPA’s findings.
To ensure comparable data, the county took 12 water samples at the same time and location that the EPA took its specimens.
The county tested both sediment and surface water for 24 metals including manganese, lead and arsenic.
Surface water samples were taken at river locations near Bakers Bridge north of Durango, Memorial Park, the drinking water intake and Dallabetta Park.
Sediment was tested at East Mesa, the Citizens Animas Ditch headgate and downstream, and the Twin Rocks Ditch headgate and downstream.
Samples were collected Aug. 15 and 16.
Wright Water Engineers Vice-President Pete Foster was charged with interpreting the county results, and reported them to be consistent with EPA and Colorado Department of Public Health and Environment reports, although the county’s levels came back slightly lower than the federal and state agency findings.
Foster explained the slight differences are because the county’s samples and the EPA samples were not collected as “true split samples.”
In other words, the county collected samples at the same time and place as the EPA, but separately. Procedure for a split sample entails collecting the water in one container, then separating it into two containers.
“At this very low level, we’re at parts-per-billion, and it’s easy to have variation, but all the samples are in concurrence with what the EPA and CDPHE released, and they meet standards,” Foster said.
“Detection levels are so low, one speck will change the results at this level.”
County results were below detection limits for lead and arsenic for dissolved constituents.
Like the EPA’s, the county’s dissolved manganese concentrations exceeded state health department health warning levels for drinking water at the Bakers Bridge sampling site on Aug. 15 and 16.
Overall, findings show water does not breach health-based standards for drinking water. Soil standards also meet recreational screening levels.
Commissioner Julie Westendorff questioned how precipitation should impact future monitoring efforts.
“I look at it and assume these numbers will stay basically the same, with some fluctuation unless you have a big rain, like we had over this past weekend,” she said.
She added that she would be more interested in monitoring levels on days that weather and runoff might impact the river.
“During high-runoff events, sediments get stirred up and redeposited,” Foster said, which isn’t necessarily negative. Even if sediment is stirred up, he said, the metals will remain below levels reported immediately after the Aug. 5 incident.
He advised continued monitoring of the Bakers Bridge area north of Durango and near Oxbow Park. Both areas are flat and more likely to collect deposits.
La Plata County’s samples were analyzed at an Albuquerque-based lab. The county also tested samples on Aug. 13-14 and Aug. 17-18, but has not yet compared those findings with EPA data.
jpace@durangoherald.com
EPA Interim Guidance Plan (PDF)
EPA’s latest results
As La Plata County reviewed the results from its independent testing, the Environmental Protection Agency released its latest set of results measuring 24 metals, including surface water and sediment testing, from sampling done at the end of August and on Sept. 1,-3.
“For each metal, the trend graphs illustrate that concentrations are significantly lower than (Recreational Screening Levels),” the EPA said in its news release on Tuesday. “The graphs also show that concentrations for all 24 metals in surface water are consistent with pre-event conditions.”
Visit www2.epa.gov/goldkingmine/gold-king-mine-data-september-8-2015 to learn more.
